In general, to define a specification for a wireless communication system, a signal to noise ratio (SNR) required for the reception is measured by conducting a simulation on a service to support or on a modulation and coding scheme (MCS) level under assumed channel conditions. Thus, a constellation error or an error vector magnitude (EVM) required at a transmitter is determined. Herein, the required EVM indicates a magnitude of the constellation error at the transmitter regardless of the channel and a receiver, which is caused by adjacent channel interference from an adjacent frequency allocation (FA), quantization based on a fixed-point design, phase noise of a radio frequency (RF) device of the transmitter, and nonlinearity of an amplifier (AMP). Unlike the SNR, the required EVM exhibits no enhancement even when the transmit power is increased. Accordingly, it is necessary to define the required EVM in the specification of the transmitter. Next, the supportable MCS level, a guard band, an FA structure, and an RF equipment requirement are determined.
A specification of the Institute of Electrical and Electronics Engineers (IEEE) 802.16e system demands the required EVM of −15 dB ˜−30 dB to support modulation schemes ranging from quadrature phase shift keying (QPSK) to 64 quadrature amplitude modulation (QAM). Yet, the modulation scheme is not distinguished in the resource allocation. That is, a certain modulation scheme should support every resource. To this end, the guard band and the RF equipment are designed to meet the require EVM −30 dB of the maximum MCS level.
As discussed above, to support the maximum MCS level in every resource region, the number of available subcarriers decreases as the guard band becomes wider. Further, in response to the increasing demands for the broad band in a next-generation wireless communication system, when a plurality of FAs is bundled or the bandwidths are overlaid, the degradation of the resource allocation efficiency because of the wide guard band is inevitable.